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K Resch

Publications and source records attributed to K Resch.

At least 55 records · Page 3Linked to original sources
PubMed1989

Characterization of the interleukin-1-induced tyrosine phosphorylation of a 41-kDa plasma membrane protein of the human tumor cell line K 562.

A 41-kDa protein, which was specifically phosphorylated upon incubation with natural purified murine interleukin 1, was recently identified by us [Martin, M., Lovett, D. H. and Resch, K. (1986) Immunobiology 171, 165-169] in highly purified plasma membranes from the human tumor cell line K 562. An in vitro assay was used to investigate and characterize the phosphorylation induced by interleukin 1, possibly involved in signal transduction and generation. Plasma membranes were incubated with radiolabeled ATP in the presence of purified natural murine interleukin 1, or recombinant human interleukin 1 alpha and the pattern of phosphoproteins was studied after separation by SDS/PAGE and subsequent autoradiography. A 41-kDa protein (pp41) was specifically phosphorylated on a tyrosine residue in the presence of interleukin 1 in a dose- and time-dependent manner. The protein showed a weak background phosphorylation in the absence of monokine. Phosphorylation took place very efficiently at 0 degrees C, whereas phosphatases were not active at that temperature. At 37 degrees C, a rapid dephosphorylation was observed which was inhibited specifically by Zn2+ and vanadate. The interleukin-1-specific induction of the phosphorylation could also be observed after detergent solubilization of the plasma membranes. Affinity labeling with an ATP analogue revealed an ATP-binding and cleaving site at 41 kDa. Interleukin 1 did not induce the phosphorylation of p41 in plasma membranes obtained from a subclone of K 562, which did not respond to interleukin 1 with growth inhibition, as was reported recently for the K 562 mother line [Lovett, D. H., Kozan, B., Hadam, M., Resch, K. and Gemsa, D. (1986) J. Immunol. 136, 340-347]. These data suggest that the interleukin-1 receptor is functionally linked to a protein-tyrosine kinase, which is implicated in its biological function.

Amino Acids↗
PubMed1989

Glomerular mesangial cells in local inflammation. Induction of the expression of MHC class II antigens by IFN-gamma.

Glomerular mesangial cells (MC) were isolated from rats and cultured for a prolonged period of time, resulting in a homogeneous cell population. MC were characterized as belonging to the smooth muscle type. They were negative for MHC class II expression. IFN-gamma and TNF alpha suppressed the proliferation of MC, demonstrating receptors for these cytokines on MC. IFN-gamma or TNF alpha, respectively, enhanced basal MHC class I Ag expression of proliferating cells in culture. The combination of the two cytokines yielded stronger effects. IL-1 beta was ineffective in enhancing MHC class I Ag expression, although MC possessed receptors for this cytokine. IFN-gamma dose dependently induced the expression of MHC class II Ag, while TNF alpha or IL-1 beta were ineffective alone. The combination of IFN-gamma with TNF alpha or IL-1 beta resulted in an enhanced induction of MHC class II Ag, compared to IFN-gamma administration alone. These findings suggest that proliferating mesangial cells of the smooth muscle type may participate in local inflammatory responses or substitute for macrophages by meeting the accessory cell requirement in the interaction with T lymphocytes. Furthermore, the data have important implications for the evaluation of the role of mesangial cells in autoimmune disease of the kidney.

Animals↗
PubMed1989

Effects of nucleotides on the activity of phospholipase C in rabbit thymus lymphocytes. Differences in assays using endogenous [3H]inositol-prelabeled membranes or exogenous [3H]phosphatidylinositol 4,5-bisphosphate as substrate.

The influence of nucleotides and pyrophosphate on phospholipase C from rabbit thymocytes was investigated by using two different methods for the determination of phospholipase C activity. In a first approach the release of radiolabeled inositol phosphates from [3H]inositol-labeled membranes was examined. By a second type of experiment the cleavage of exogenously added radiolabeled phosphatidylinositol 4,5-bisphosphate (PtdIns-4,5-P2) was measured. Using internally labeled membranes only guanosine 5'-O-(thiotriphosphate) exhibited a stimulatory effect on the phospholipase C suggesting the involvement of a G-protein. When exogenous [3H]PtdIns-4,5-P2 was used as substrate, cleavage of PtdIns-4,5-P2 was stimulated by all nucleotides investigated; in addition pyrophosphate showed a stimulatory effect. From these data we conclude that the increased cleavage of exogenous PtdIns-4,5-P2 induced by GTP analogues is not conclusive in terms of the involvement of a G-protein. Rather than induced by a G-protein this activation may be caused by an increased substrate accessibility. Our experiments with endogenous substrate clearly established the regulatory role of G-proteins for membrane-bound phospholipase C.

Adenosine Triphosphate↗
PubMed1989

Cholera toxin modulates the T cell antigen receptor/CD3 complex but not the CD2 molecule and inhibits signaling via both receptor structures in the human T cell lymphoma Jurkat.

The human T cell lymphoma Jurkat can be activated by stimuli directed either against the T cell antigen receptor-CD3 antigen complex (TcR/CD3) or the CD2 molecule. Stimulation of cells via the TcR/CD3-complex or via the CD2 molecule increases inositol phosphates and cytoplasmic free calcium. Pretreatment of Jurkat cells with cholera toxin leads to a decrease of TcR/CD3 expression on the surface of the cells, while the expression of CD2 is unaffected. In contrast to this distinct effect on the receptor expression, signaling via both pathways is inhibited by cholera toxin. The most convincing explanation for the cholera toxin-mediated inhibition of signaling is that cholera toxin interrupts the signaling pathways at a point where both, stimulation via TcR/CD3 and via CD2, use the same route. The earliest common point of the two signaling pathways, at least in the Jurkat cell line, seems to be the CD3 complex because after its down-regulation (and functional inactivation) both pathways of activation are interrupted.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1989

Differential effect of dexamethasone on the regulation of phospholipase A2 and prostanoid synthesis in undifferentiated and phorbolester-differentiated U937 cells.

The human undifferentiated histiocytic cell-line U937 can be induced to differentiate by incubation with 12-0-tetradecanoylphorbol-13-acetate (TPA) into macrophage-like cells. Dexamethasone reduced the prostaglandin production in TPA-differentiated U937 cells dose dependently, whereas undifferentiated U937 cells were dexamethasone insensitive. Concomitantly phospholipase A2, the enzyme liberating the prostaglandin precursor arachidonic acid, was inhibited by dexamethasone in TPA-differentiated but not in undifferentiated U937 cells. The activity of lysophosphatide acyltransferase, the key enzyme of fatty acid reacylation into phospholipids, remained unchanged both in undifferentiated and TPA-differentiated U937 cells. The data suggest that responsiveness to glucocorticoid-dependent regulation of prostanoid synthesis is acquired by cells of the monocyte-macrophage lineage late in differentiation.

Acyltransferases↗
PubMed1989

Virus-transformed macrophage-like cell line as tool for eicosanoid research.

The ability of a virus-transformed murine macrophage like cell line HA 38 to produce different eicosanoid metabolites was examined. HA 38 cells release similar amounts of prostaglandins and leukotrienes as did murine peritoneal macrophages in response to both physiological and non-physiological stimuli. Enzyme systems known to be involved in the regulation of eicosanoid synthesis are expressed. HA 38 cells thus are a well defined macrophage model system and are well suited to study eicosanoid synthesis in macrophages and effects of drugs on the prostaglandin and leukotriene synthesis pathways.

Animals↗
PubMed1989

Glucocorticoids inhibit prostaglandin synthesis not only at the level of phospholipase A2 but also at the level of cyclo-oxygenase/PGE isomerase.

1. Prostanoid synthesis was induced in bone marrow-derived macrophages by addition of exogenous arachidonic acid to the cell cultures. When the cells were preincubated with dexamethasone (10(-7) and 10(-6) M) overnight, prostaglandin synthesis was inhibited by 66.5 +/- 2.8% and 56.7 +/- 2.9% (mean +/- s.d.; n = 3) respectively. 2. Endogenous membrane bound phospholipase A2 was measured with labelled phospholipids used as substrates. The enzyme activity with phosphatidylcholine and phosphatidylethanolamine as substrates was inhibited by 27.0 +/- 8.3% and 23.3 +/- 11.1% (n = 4) respectively, in dexamethasone-treated macrophages compared to control cells. Neither the distribution of radiolabelled arachidonic acid among the different phospholipid species nor the release of arachidonic acid from prelabelled cells were significantly impaired by pretreatment of the macrophages with dexamethasone (1 microM). 3. The enzyme activity of the cyclo-oxygenase/prostaglandin E (PGE) isomerase was measured in cell membranes from control cells and dexamethasone-treated cells. It was inhibited by 40.0 +/- 8.4% (n = 4) in dexamethasone-treated cells as compared to control cells. Thus, glucocorticoids inhibit not only phospholipase A2 in these cells, but predominantly inhibit arachidonic acid metabolism subsequent to its release from phospholipids.

Animals↗
PubMed1989

Aluminium fluoride enhances phospholipase A2 activity and eicosanoid synthesis in macrophages.

Eicosanoid synthesis in macrophages is controlled by the availability of free arachidonic acid. Activation of the phospholipase A2 (PLA2) is an important mechanism leading to increased eicosanoid synthesis. In order to obtain further insight into the regulatory mechanisms of eicosanoid release, we incubated macrophages with the protein kinase C (PKC) activator dioctanoylglycerol (DiC8) or aluminium fluoride (AIF4-), a well-described activator of guanine nucleotide binding proteins (G-proteins). Arachidonic acid release, membrane-bound PLA2 activity and prostaglandin production in macrophages were enhanced by both substances in a time-dependent manner. Incubation with the phorbol ester TPA had no effect on the PLA2-activity. AIF4- elevated the cellular diacylglycerol content. The results suggest that activation of PLA2 and successive eicosanoid synthesis by AIF4- is mediated by direct activation of PLA2 by the AIF4(-)-induced generation of diacylglycerol.

Aluminum↗
PubMed1989

TPA-induced differentiation and adhesion of U937 cells: changes in ultrastructure, cytoskeletal organization and expression of cell surface antigens.

Incubation of the human promonocytic cell line U937 with 12-O-tetradecanoylphorbol-13-acetate (TPA) for 72 h resulted in differentiation into immature macrophage-like cells and was accompanied by marked morphological and functional changes. U937 cells which normally grow in suspension and show a smooth surface, extended pseudopodia and became adherent to each other and to the surface of the culture vessel. Concomitant with the TPA-induced adherence U937 cells ceased to proliferate. Our results show that phorbol ester-treated U937 cells exhibited markedly increased levels of fibronectin and of the cytoskeletal proteins actin, myosin and vimentin including a reorganization of actin and vimentin filaments. The induction of both cellular adherence and growth inhibition were accompanied by a significantly reduced level of cells expressing transferrin receptors and changes in cell surface antigen expression. Here, the expression of the leukocytefunction antigens (LFA-1), including CD11 and CD18 was markedly enhanced during phorbol ester-induced differentiation. TPA-treatment, however, failed to enhance the small amount of U937 cells expressing the monocyte/macrophage-specific CD14 antigen or expressing MHC class-II antigens. A detailed analysis of the CD14 cluster by 7 differential antibodies resulted in an induction of TM1, UCHM1, MEM15, My4, and 3C10, whereas the epitopes recognized by TM2 and Mo2 remained unaltered. Neither indomethacin nor interferon-gamma were capable of inducing a marked expression of these antigen epitopes in TPA-treated cells. Although these data demonstrate that during phorbol ester-induced differentiation U937 cells acquire many properties typically associated with macrophages, the failure to express marked levels of macrophage-specific cell surface antigens suggests a transition of U937 cells from a promonocytic to an immature macrophage intermediate state rather than into mature macrophage-like cells.

Antigens, Surface↗
PubMed1988

Phospholipase C in rabbit thymocytes: subcellular distribution and influences of calcium and GTP gamma S on the substrate dependence of cytosolic and plasma membrane-associated phospholipase C.

The subcellular distribution of phospholipase C (PLC) activity in rabbit thymocytes was examined by measuring the enzyme's activity in different subcellular fractions. PLC activity was determined using exogenously added [3H]PIP2 as substrate. Approx. 80% of the activity of the cell homogenate was found in the cytosolic fraction. A minor portion of PLC activity was attached to the particulate fraction. This membrane-associated PLC activity was found to be predominantly bound to the plasma membrane. Both PIP2-cleaving PLCs (the PLC associated with the plasma membrane and the PLC in the cytosol) exhibited maximum activity at pH 5. GTP gamma S stimulated the cytosolic and the membrane-bound PLC. As revealed by computer analysis of the substrate dependence of both basal and GTP gamma S-stimulated PLC activity, GTP gamma S enhanced the Vmax of the enzymes. Calcium, at a concentration of 1 mM, decreased PLC activity, as compared to a calcium concentration of 100 nM. The characteristic increase in Vmax induced by GTP gamma S was observed at a concentration of 1 mM calcium and was similar to that at 100 nM. These data suggest that the stimulatory effect of GTP gamma S is not due to an increased affinity of PLCs to calcium.

Animals↗
PubMed1988

Zinc increases the affinity of phorbol ester receptor in T lymphocytes.

In the primary structure of the major phorbol ester receptor, protein kinase C the presence of putative metal (zinc) binding sites has been suggested. We have demonstrated earlier that zinc activates protein kinase C and contributes to its binding to plasma membranes in T lymphocytes. Here we report that zinc increases the phorbol ester binding affinity of cytosolic protein kinase C. The effect of zinc on the membrane-bound enzyme is much less pronounced. Our results raise the possibility that cytosolic protein kinase C is a mixture of isoenzymes with different sensitivity towards zinc ions.

Animals↗
PubMed1988

Zinc can increase the activity of protein kinase C and contributes to its binding to plasma membranes in T lymphocytes.

In the primary structure of protein kinase C, the presence of a putative metal-binding site has been suggested (Parker, P.J., Coussens, L., Totty, N., Rhee, L., Young, S., Chen, E., Stabel, S., Waterfield, M.D., and Ullrich, A. (1986) Science 233, 853-859). In the present report, we demonstrate that the most abundant intracellular heavy metal, zinc, can increase the activity of cytosolic protein kinase C. Zinc reversibly binds the enzyme to plasma membranes, and it may contribute to the calcium-induced binding as well. The intracellular heavy metal chelator N,N,N',N'-tetrakis(2-pyridylmethyl) ethylenediamine prevents the phorbol ester- and antigen-induced translocation of protein kinase C. This effect can be totally reversed by the concomitant addition of Zn2+, while Fe2+ and Mn2+ are only partially counteractive. Our results suggest that zinc can activate protein kinase C and contributes to its binding to plasma membranes in T lymphocytes induced by Ca2+, phorbol ester, or antigen.

Animals↗
PubMed1988

Biological properties of dihydro-leukotriene B4, an alternative leukotriene B4 metabolite.

Dihydro-leukotriene B4 (a 5,12-dihydroxy-eicosatrienoic acid) has been shown to be the primary metabolite of leukotriene B4 (LTB4) in a variety of cells other than human polymorphonuclear leukocytes (PMNLs). In this report we show that dihydro-LTB4 is significantly less active than LTB4 in different biological assay systems, i.e. leukocyte chemotaxis, chemokinesis, aggregation, adhesion to endothelium and superoxide anion production. This suggests that primary reduction constitutes a second so far unknown deactivation pathway for LTB4.

Cell Adhesion↗